1. Field of the Invention
This invention relates to a work cylinder having a damping movement limit. Such a work cylinder may be used, for example, as the work cylinder of a rodless piston cylinder. Such a work cylinder typically has cylinder covers closing off the ends of the cylinder, and the piston is generally slidable within the cylinder, with the amount of movement within the cylinder being limited by position stops or limits. These stops or limits can be damping stops or limits which also absorb some of the shock produced by contact of the piston with the stop or limit.
2. Background Information
The prior art includes numerous examples of pneumatic work cylinders which have damping limits for damping and limiting movement of the piston within the cylinder. Essentially, a distinction can be made between two different types of damping. The first type of damping is typically referred to as dynamic damping, and the second type as impact damping.
In dynamic damping, the piston movement is damped as a function of its velocity, several millimeters, or even centimeters before it reaches the limit stop point. Such dynamic damping can be achieved by having a damping piston, which can be located either on the cylinder cover or directly on the work piston itself, penetrate, at the end of the work stroke, into a compression chamber provided with a sealing ring. Such a compression chamber is typically forcibly vented, but only after the pressure build up within the chamber reaches a predetermined pressure limit.
Such a damping limit is described in the advertising brochure published by the firm of Miller Fluid Power (File 8625 018909). In the Miller cylinder, a stationary plunger located in the limit stop, penetrates into a corresponding recess in the work piston. The recess has a corresponding sealing ring, and as the piston penetrates into the recess, the volume of the recess is compressed, so that a deceleration of the piston takes place as described above. A disadvantage of this version of the prior art is that the damping plunger must be attached to the cylinder cover by appropriate fastening elements. During the fastening, close attention must be paid to a precise positioning of the damping plunger since the work piston determines the precise position of the damping plunger in the vicinity of the limit stop. This type of precise positioning assembly generally increases the expense and complexity of assembly and installation.
The second possibility for limit damping is typically referred to as impact damping. One version of this type of damping limit is described in the advertising brochure published by the firm of Sudtechnik, Maroldt & Co. KG (Publication No. 7812). The impact damping in this prior art device, called a "Mardrive" Pneumatic Linear Transporter, is accomplished by means of bumpers disposed on the end surfaces of the cylinder. A disadvantage of this arrangement, like the previous arrangement of Miller, is that the damping stops called bumpers must also be fastened in place with fastening elements during assembly and installation.